Method and arrangement for the production of stereoacoustic photo films



April 1929- r i F, SCHROETYER 1,708,523

METHOD AND ARRANGEMENT FOR THE PRODUCTION OF STEREO ACOUSTIC PHOTO FILMSFile d June s, 1926 vwentoz FR\TZ SCHROETER 351 his flbhomug Z aPatented Apr. 9, 1929.

UNITED STATES I 1,708,523 PATENT I OFFICE- FRITZ SGHROETER: OF BERLIN,GERMANY, ,ASSIGN'OR TO GESELLSCHAFT FOR BRAKE- LOSE TELEGRAPHIE M. B.H.,'OF BERLIN, GERMANY, A. CORPORATION OF GERMANY.-

METHOD AND ARRANGEMENT ron THE rnontro'rIoN or STEREOACOUSTIC rnoro IFILMS. v 1/ Application filed. June 5, 1926, Serial No. 113,890, at inGerniany June 22,1925.

The object of my invention is to use the ence being governed by thephase angle within which the sound source is localized by the auditorysenses. According to my invention it is possible to obtain suchstereo-acoustio audition in the reproduction of sound phe nomena withthe use of phono-films as intermediary means.

The invention, more particularly speaking, consists in the doublephotographic recording of the sound waves upon the film, .whereby theacoustic phenomena are recorded twice. The invention can be carried intopractice, for example, by recording the two low frequency phenomena insynchronism,

. by the co-action of which binaural or plasmounted and secured at theproper relative" tic audition is produced. In this recording,

each record or illumination device which causes such a record iscoordinated to a separate microphone, or a separate group ofmlcrophones. Each microphone 1s so position that it may be caused to actwith the proper time difference upon the controlling luminous sourcesprovided for making the record of the sound waves.

It can thus be seen that the position of the two microphones in relationto the sounds detected corresponds to the position of the ears of ahuman being, so that the sound reception maybe similar to that receptionobtained by a person positioned at the point.

' In the reproduction of the sound, by my invention I also use a dualsystem, for example, two photo-electric cells which are each influencedby the phono-iilni produced.

in the recording process. By means of amplifiers the'photo-electriccells are brought to act upon loud speakers mounted at appropriatepoints in the room, or else upon head sets, in such a manner that one ofthe telephone receivers is influenced by the action of the firstphoto-electric cell, and the other receiver influenced by the secondphoto-electric cell;

Other objects'of my invention are to produce an arrangement forproducing binaural auditionin which there is a relatively simpleconstruction and arrangement of parts, efficient operation, and arelatively small in- I stallation expense.

Still other objects will be apparent from' the following description andclaims when read in connection 'with the accompanying drawing, showinggreatly simplified diagrams of my arrangement, wherein:

d Fig. 1 shows, by way of example, an equipment for making the records;and

Fig. 2shows an exampleof a means for reproducing the acoustic phenomena.

4 Referring first to the production of the records, as illustrated byFig. 1, two microphones 1 and 2, each fed from a common en-. ergy source3 are placed at difierent relationship to the sound source (which may beassumed to be at a point S) in accordance with the requirements ofstereo-acoustic audition. The oscillations produced in the microphones 1and 2 by theincoming soundimpulses are carried through transformers 4.and 5, respectively, to amplifiers 6 and 7 where the potential israised.- The raised potential is then carried to the Kerr cells 8 and 9where it is used to control the voltage on the plates of the said cell.

The voltage control on the plates of the Kerr cells, inconjunction withthe corresponding optical polarization means, well known in connectionwith this type of cell,

consisting of a condensing lens 10 to direct vided up into ahorizontaland a vertical component, and when this light passes betweenthe plates of the Kerr cell the vertical component of the light iseither speeded up or slowed down with respect to thehorizontalcomponentJ-depending upon whether the plate voltage on thecell is either increased or decreased.

The resultant component of the vertical 1 and horizontal wave is thuschanged into .a difierent plane of polarization, and this is madeevident when passing through the analyzing Nicol prism set at rightangles to ,the bands 15 and 16 of 30' the first for were the plane notchanged, all the light would be blocked out as. the second Nicol has thesame property as eliminating all light active in one direction. Theincrease or decrease of voltage is, of course, dependent upon the energysupplied in the microphone and amplified by the amplifiers 6or 7. Sincethe microphones are usually not in the same, relative position to thesound source, aslightly different effect will be produced in each cellat the instantaneous time, for the same effect can only be produced whenthe sound impulses in each microphone are exactly in the same angularphase relationship. As above stated, the polarized light coming to thecell from the light source is weakened to a greater or lesser extent atthe rhythm of the oscillations of speech or other sound which is tobetransmitted.

In the path of the rays passing through the Kerr cell and the secondNicol prism 11*, I place a lenslO to direct the light ray to a film ltcomprising a pair of phone-film bands 15 and (16 band 15 beingcoordinated to microphone 1 and Kerr cell 8 and band 9 coordinated tomicrophone 2 and Kerr cell 9. The ray pencils 12 and 13 produce upon thefilm 14 lighter or darker images of the slit of the respective Kerrcells depending upon the voltage strength on the plates of the'saidcells. The oscillations are thus recorded, in synchronism, but displaced.with reference to time, in conformity with the actions upon'the twomicrophones, as above stated.

'In reproducing, as shown by Fig. 2, two light sources 17 and 18, incombination with suitable optical auxiliaries, as lenses 19 and 20,project slit-like-images through the bands 15 and 16 of the film 14 uponthe photoelectric cells 21 and 22. The photo-electric cells 21 311(1922are supplied with energy from a joint battery 23, and the variations incurrent occasioned by brighter and darker stripes amplifier tubes 25 and26. From this point the current is amplified and brought to receivers 27and 28, which, similar to the microphones 1 and 2, are disposed andconnected in conformity with the requirements of plastic soundreproduction. means the travelling film produces a correspondingaudition or auditory perception to that of the microphones. i

The optical pathof the rays is shown with certain diagrammaticsimplification, for the f true proportions have been left out ofconsideration in order to simplify the illustration and to make it morereadily understood.

If desired, the plastic properties in the reproduction can be furtherimproved by the use of additional microphones, the latter beingplaced atthe pro er points with relation to the others, an the recording of a orbands on the film are :fed to the b By this ber of reproducingapparatus. The form in which the acoustic phenomena are recorded andmarked upon the film, and the light controlling means used therefor'areimmaterial, so'far as thefundamental features of this invention areconcerned. geous, however, to operate .with means of this kind being asfree from sluggishness and working as quantitatively as possible, forinstance, by having recourse to the Kerr effect (electric doublerefraction in a condenser filled with a suitable medium for examplenitro-benzol) in order that the higher frequencies, especially in thecase of music, may not be impaired. 1

The idea of the Kerr efl'ect, per se, is old and has been explained ingreater detail in each of the following publications, Theory of'Light-Preston1912, page 445 and following, and in vol. 1 of thePhilosophical Magazinepages 337 to 446.

,While I have herein shown and described only one form of my invention,other modi fications may be made without departing from the spirit andscope of the invention as defined by the appended claims.

Having described my invention, I claim:

1. A binaural system for recording sound which includes, a plurality ofspaced sound pick-up devices, an amplifying means associated with eachof said sound pick-up devices, electrostatic means connected with eachof said amplifiers and receiving potentials from said amplifiers inaccordance with the intensity of sound reaching the amplifier, a lightsource associated with each of said electrostatic devices, means forpolarizing the light from said source and directing the same throughsaid electrostatic devices, and means controlled by the potentialsapplied to said electrostatic devices for doubly refracting said planepolarized light cam in accordance with the sound received at each ofsaid sound pick-up devices, and a light sensitive film for'recording'the light passing through said electrostatic device.

2. The system claimed in claim 1 comprising in addition, means forreproducing the sound thus recorded on said light sensitive filmincluding, a pair of photo cells subject to light intensities varied inaccordance with the record on said film, and a pair of sound reproducerscontrolled from said photo cells or reproducing the sound effects heardat the said sound pick-up device and producing binaural effects upon theears of a listener at the point of reproduction.

3. A system for producing binaural effects upon a light record whichincludes, means provided at points separated a distance from each otherso as to receive sound impulses both in phase with each other andslightly It is advanta.

pendently associated with each of said sound pick-up devices, a Kerrcell connected with out of phase with each other depending upon thelocation of the sound source for receiving sound impulses and detectinga phase and'time difference in the sound waves thusrecei'ved, anamplifying means. indeeach 'of said amplifiers, a light sourceassociated with each of said Kerr cells, means for polarizing the lightfrom said source and directing the same between the lates of said Kerrcell, and means provided y said Kerr cell and governed in accordancewith the potentials produced upon' said Kerr cell from said amplifierfor controlling the said in accordance with the sound waves impressedupon said sound pick-up device, and a light sensitive recording strlpassociated with said Kerr cells for producing thereon a double record ofthe sound received wherein each record difi'ers from the other at afixed and predetermined point by a phase difi'erence similar to thephase difference of the sound received at .the'said sound pick-updevice.

' FRITZ soHRoETER.

15. polarized light beam passing therethrough Q

